1. Field of the Invention
The present invention relates to the structure of an exposed terminal portion of a solar cell module and more particularly to the technology for improvement in moldability, strength, and reliability after installation, of a terminal box attached to the solar cell module.
2. Related Background Art
In general, in solar cell modules, terminal boxes are normally bonded to portions thereof intended for output extraction in the back surface of a solar cell module with an adhesive such as silicone resin or epoxy resin and the positive and negative output lines are guided out of terminal boxes. Each external output line is mechanically connected or is integral with a lead wire, which is taken out from an exposed electrode portion of the solar cell, inside the terminal box.
The terminal boxes normally have such configurations as a cube, a rectangular parallelepiped, or a cylinder, as shown in FIG. 12, or as combinations thereof, and all of their side surfaces comprises a surface normal to the bonded surface.
The conventional terminal boxes do not include a terminal box having all of its side surfaces each comprising an inclined surface, as described above.
However, the terminal boxes are provided so as to protrude from the solar cell module and tend to suffer an external force during transportation, during installation, or the like. In many cases, the terminal boxes suffer the external force when the protruding portions of modules, i.e., the terminal boxes, collide with each other.
Usually the bonding strength in the shearing direction of the terminal box to the solar cell module is not less than 4 kgf, which is enough to prevent the terminal box from being changed in external appearance and in performance on the occasion of ordinary contact or collision. However, it is not inconceivable that an unexpected accident or the like would cause a terminal box to suffer the external force over the designed value and to be dismounted, thereby necessitating repair or replacement of the solar cell.
On the other hand, designing the bonding strength in the shear direction of the terminal box to the solar cell module in expectation of such cases is normally excessive.
An object of the present invention is to provide a structure of an exposed terminal portion of a solar cell module that has high strength and enhanced reliability after installation, overcoming the above drawback.
The inventor has extensively and intensively studied in order to achieve the above object and finally found that employing a configuration with a part or all of each of the side surfaces of the terminal box comprising an inclined surface makes it possible to improve the strength and reliability after installation without a need for the design of excessive bonding strength in the shearing direction, thus accomplishing the present invention.
More specifically, the terminal box of the present invention is a terminal box for covering an exposed electrode portion of a photovoltaic element module, wherein a part or all of each of the side surfaces of the terminal box comprises an inclined surface.
According to the present invention, by providing an inclined surface at a part or all of each of portions that relatively tends to suffer an external force, of each of all the side surfaces of the terminal box, ascending from the bottom to the top, the effect of relieving the external force in the horizontal direction during application of the external force in the horizontal direction is enhanced.
FIG. 13 is a view showing the relation between the terminal box and the external force exerted thereon and FIG. 15 is a graph showing a presence or absence of an external force relief effect and coefficients of friction xcexc between an inclined surface of a terminal box and an external material.
As shown in FIG. 13, when a coefficient of friction between a material of the inclined surface portion of the terminal box and the external material is defined as xcexc, the external force in the horizontal direction (referred to as xe2x80x9chorizontal, external forcexe2x80x9d in the figure) as F, and an angle of inclination of the inclined surface as xcex8, the external force in the horizontal direction can be relieved if the relation of relief force (N): F cos xcex8 greater than frictional force (M): xcexcxc3x97F sin xcex8 is satisfied.
Namely, as shown in FIG. 15, by setting the angle of inclination xcex8 of the inclined surface and the coefficient of friction xcexc so as to be in the area of relief force (N) greater than frictional force (M), the effect of relieving an external force in the horizontal direction when applied with the external force in the horizontal direction is enhanced.
However, the external material cannot be specifically limited. Even if specifically limited, the coefficients of friction thereof to the inclined surface vary depending upon the shape of surface, pressure of surface, humidity, and so on. Therefore, the angle of inclination xcex8 is preferably set small, and more preferably, it is desirable that the angle of inclination xcex8 is set to be not more than 60xc2x0.